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Old Jun 6, 2003, 8:42 AM   #1
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Default Home made 500mm Lens

Hi all, I have made an adapter to allow the use of standard 1 1/4" telescope eyepieces with fixed focal length lenses. This allows one to use the combo as an add on lens for most digicams. I can provide details to anyone intrested, I too tried many add on telextenders, and such for my two digicams, with OK results. However if you really want to reach out and capture a subject at 100 plus yards, there is nothing better than an inexpensive, generic, 500 mm telephoto lens. These can be had on E-bay for $35-$60 US. There are not top quality as far as 35mm camera lenses are concerned, however they are quite crisp, and bright. Besides did you expect ED glass for $35.00? Anyhow, a simple 1 1/4" to 1" PVC reducer, hand screwed into a T-ring from any T-mount adapter provides the eyepiece holder. I then used a bottom cap from a 1 1/4" eyepiece, cut the bottom off, to tighten the eyepiece fit. Last a simple thumb screw to provide tension on the eyepiece. Depending on your camera, an eyepiece from 40mm down to 13 or 14mm will provide anywhere frrom 12.5X for a 40mm eyepiece, up to 38.46X for a 13mm eyepiece. The ammount of vinyetting can be reduced with lower power eyepieces, and power can be increased again with standard telescope barlow lenses. You will need an eyepiece adapter to allow you to attach your camera to the eyepieces, but these too are reasonable. I actually had a machine shop make me one out of aluminum.

Casey
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Old Jun 6, 2003, 9:15 AM   #2
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can you show here?

thanks
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Old Jun 7, 2003, 12:40 PM   #3
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Hi,
i am interested in doing it...where can i get da step by step?
could u email me?

my email is [email protected]

thanks
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Old Jun 7, 2003, 12:42 PM   #4
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Default hi..step ?

Hi,
i am interested in doing it...where can i get da step by step?
could u email me?

my email is [email protected]

thanks
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Old Jun 9, 2003, 12:36 PM   #5
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Default RE:

Sorry it took me so long to reply. Been remodeling a kitchen. I will put together step by step instructions, and either post them here, or e-mail them to those that want it. Should have document ready by Wed. this week.

Casey
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Old Jun 25, 2003, 9:28 AM   #6
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Yeah, as a avid (some say rabid ) DIY'er I'd be interested in seeing the final product, a couple of pix would also be nice

Or email, [email protected]

Thanx!
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Old Jun 25, 2003, 9:28 AM   #7
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Default interesting

Sorry, I got an error and then resubmitted hence the double-post.
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Old Jul 14, 2003, 5:18 PM   #8
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Default RE Homemade 500mm lens

Hi all sorry it took me so long to repost some specifics, been finishing a kitchen remodel for the wife. Anyhow, here we go. First obtain a T-mount lens, I used a 500mm fixed focal length lens. These are available on E-bay and such from $25.00 - $75.00. I wouldn't spend any more for one of these, as they are all virtually identical. If you choose you should be able to use any T-Mount lens of your choice. I have also seen quite a few of the Mak design lenses being sold quite reasonably. Next pickup a T-Mount adapter from any camera store, preferably a used one if possiable, (lower cost). You only need the actual T-threaded ring from the adapter. Next stop by your local Lowes, Home Depot, etc and pickup a PVC 1 1/4 - 1" reducer. I cut mine with a miter saw at 25mm from the top to bottom. Next if you want your image right side up, and left to right corrected, stop by http://www.surplusshed.com/ and get one or two mounted roof prisms. Last time I checked they were $4.00 each. I then took a piece of PVC tubing, sanded the inside of it until the roof prism fits snugly. This can then be threaded into a standard 1 1/4" telescope eyepiece. NOw thread the 1 1/4 - 1" reducer into the ring from the T-Mount, you only need a couple of good turns to make it secure. This will now screw ontothe back of your telephoto lens, I also cut the bottom off of an eyepiece case and used it to tighten the fit of the Eyepiece into the adapter. Screw your roof prism mount into the bottom of a 13 - 25mm eyepiece, insert into the newly made holder, and you have, first a nice bright, very well corrected spotting scope, all you need to use this with your digicam is a simple eyepiece adapter ring, and a sturdy tripod. I had an eyepiece adapter made at a local machine shop for $45.00 in 34mm thread. [/img]
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Old Jul 14, 2003, 6:11 PM   #9
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Default Additions to homemade 500mm lens

Hello again, I just thought I would post some numbers from the homemade telephoto lens. Using a 13mm eyepiece you can expect 38.46X, with a 20mm eyepiece, 25x This is quite usable to aquire subjects at very long distances.
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